KR0140531B1 - Battery with current blocking valve - Google Patents

Abstract

None.

Description

Battery with current cutoff valve

1 to 3 are structural diagrams of a conventional explosion-proof battery.

4 is a characteristic diagram in a conventional overcharge test.

5 and 7 are structural diagrams of the battery of the present invention.

6 is a characteristic diagram in an overcharge test of the battery of the present invention.

8, 9, and 10A are structural diagrams of another battery of the present invention.

10B is an enlarged view illustrating main parts of FIG. 10A.

11 is a cross sectional view along line II-II of FIG. 10A.

12A to 12C are explanatory views of the assembling procedure of the safety device of the present invention.

13 is an explanatory diagram of a moving state of the safety device of the present invention.

14 to 19 are X-ray diffraction pattern diagrams of the anode material of the present invention.

20 is a characteristic diagram showing a relationship between battery voltage and battery breakdown voltage.

* Explanation of symbols for the main parts of the drawings

1: outer tube 2: gasket

4: stripper 8: lead plate

30: intermediate fitting member

[Background of invention]

TECHNICAL FIELD The present invention relates to an explosion proof enclosed cell having an explosion proof structure, and also to an organic electrolytic secondary cell having such a structure.

In recent years, the use of secondary batteries such as lithium batteries and carbon lithium batteries for video tape recorders, watches, and the like has been considered.

By the way, in the battery as described above, the power generation elements contained in the battery cause chemical changes, increase the internal pressure, and cause explosion. For example, when an abnormal current is usually supplied to a non-aqueous electrolytic cell, such as a lithium secondary battery, so that a so-called overcharge state or a short circuit state occurs due to misuse, a large current flows, and the electrolyte is decomposed to form a gas. This gas may be filled in turn, and the pressure in the battery may increase, resulting in an explosion.

Thus, in order to prevent the explosion of the battery as described above, as shown in FIG. 1 or FIG. 2, an explosion-proof device is used on the upper end side of the outer tube 41 which also serves as a negative electrode terminal accommodating the power generating element. A safety valve device is installed.

Specifically, the safety valve device shown in FIG. 1 is attached to the upper surface of the insulating gasket 42, and the cover plate 44 and the concave portion in which the valve hole 43 is drilled in the center thereof. A recess 45 is formed and attached to the sea surface to cover the upper portion of the cylindrical elastic valve body 47 formed of a thin portion 46 and the upper portion of the elastic valve body 47. 48 is formed of a plate-shaped terminal plate 49, the cutting portion 50 is formed in the concave portion 45 of the elastic valve body 47 is formed with a cutting blade 50 protruding in the direction of the thin portion 46 The member 51 is provided.

According to the battery, when the power generation element contained in the outer tube 41 causes a chemical change, and the internal pressure of the outer tube 41 is increased, the thin portion 46 of the elastic valve body 47 is a cutting member. It extends in the cutting blade 50 direction provided in the 51. When the thin thickness portion 46 abuts on the cutting edge 50 and the internal pressure increases, the thin thickness portion 46 is destroyed by the cutting edge 50, and is drilled by the plate-shaped terminal plate 49. The gas is exhausted into the atmosphere via the exhaust gas discharge hole 48 to prevent battery explosion.

In addition, the safety valve device shown in FIG. 2 is inserted into and supported by an insulating gasket 61 and has an intermediate lid 69 having a thin thickness portion 62 formed into a groove extending radially from the center, and an outer tube. It is comprised by the obstruction lid 64 which closes 41. Reference numeral 65 denotes a power generator that constitutes a power generation element, and is wound in a tubular shape on the core 66 with separators in which the negative electrode material and the positive electrode material infiltrate the electrolyte solution. Further, reference numeral 67 is a lead terminal, one end of which is attached to a cathode wound in a tubular shape, and the other end of the lower side of the middle lid 63 passing through the through hole 69 from the bottom surface of the insulating plate 68. It is attached to the surface by welding. Reference numerals 70 and 71 are gas discharge holes that penetrate the gas generated from the power generation element out of the cell.

According to the battery, a gas is generated by chemical change of the power generation element. When the internal pressure of the outer tube 41 is increased by this gas, the intermediate lid 63 gradually protrudes toward the occlusion lid 64. When the internal pressure rises, as shown in FIG. 3, it bursts from the position of the thin thickness part 62 formed in the intermediate lid 63. As shown in FIG. Due to this rupture, the gas filled in the outer tube 41 is discharged from the rupture position in the direction of the obstruction lid 64, and thereafter, the gas is expelled from the gas discharge holes 70 and 71 to the atmosphere. Is prevented.

However, in the conventional explosion-proof sealed battery as shown in FIGS. 1 and 2, the safety valve (an elastic valve body 47 in the battery shown in FIG. 1, and an intermediate in the battery shown in FIG. 2) When the lid 63 ruptures, the increase in the internal pressure is suppressed, but since the charging current continues to flow, the decomposition of the electrolyte and the active substance in the battery proceeds again, and the temperature continues to rise accordingly, leading to the last ignition. Fig. 4 shows changes in battery voltage, charging current, and battery temperature over time until the battery ignites when the overcharge state is continued (curves IV, V, and VI, respectively, for battery pre-arm and charge). Current, battery temperature).

This phenomenon also occurs in the case of a short circuit. In other words, the short-circuit current continues to flow even after the safety valve is opened and the internal pressure rises, so that the temperature rises and eventually ignites.

In addition, due to the cleavage of the safety valve, there is also the inconvenience that the electrolyte leaks out of the battery via the cleavage portion and the gas discharge hole.

[Purpose of invention]

The present invention has been made in view of such a point, and an object thereof is to provide an explosion-proof sealed battery which can prevent ignition and rupture caused at the time of overcharging or short-circuit with a simple configuration and also prevent leakage of electrolyte. .

In addition, the present invention provides a structure for improving the workability of assembling the current cutoff valve in a battery having a current cutoff valve in the battery operated by an increase in the internal pressure at the time of overcharging for the above-described purpose.

In addition, the present invention is to provide a battery such that the current cutoff valve is operated reliably before the battery breaks down so that the internal pressure due to overcharging does not increase rapidly, and the battery is destroyed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described with reference to FIGS. 5 to 7.

The explosion-proof sealed battery according to the present embodiment includes a cylindrical outer tube 1 in which a power generating element is housed, a gasket 2 provided on an inner circumference of the upper end side of the outer tube 1, and the like. An explosion-proof valve 3 serving as an intermediate lid inserted into and supported by the gasket 2, a stripper 4 provided in contact with the lower surface of the explosion-proof valve 3, and the exterior pipe 1; The gasket (2), the explosion-proof valve (3), and the occlusion lid (5) are caulked and attached to the outer tube (1).

In the outer tube 1, a negative electrode material (for example, a metallic lithim foil) and a positive electrode (for example, a positive electrode substrate coated with molybdenum emulsion) are fitted with a separator in which an electrolyte is infiltrated. A power generating body 6 formed by winding a tubular shape on the core 21 is stored as a power generating element, and a sheet-shaped insulating plate 7 is formed on the top of the power generating body 6. A through hole 10 for penetrating the lead terminal 9 extending from the lead plate 8 is formed in the center portion of the insulating plate 7. This lead terminal 9 is attached to the positive electrode material which is bent from the lead plate 8 and wound in a cylindrical shape. The lead plate 8 is connected to the lower surface of the projection 3a of the explosion-proof valve 3 described later, which is directed downward from the through hole 10 of the stripper 4 described later by a method such as ultrasonic welding. At this time, the lead plate 8 is in a state in which legs of the lower surface of the stripper 4 and the projections 3a of the explosion-proof valve 3 cross each other.

On the other hand, a large diameter portion 12 is provided on the upper end side of the outer tube 1 in which the power generating element is stored, and the gasket 2 is fitted into the large diameter portion 12. The gasket 2 seals the inner circumference of the shell tube 1 to prevent leakage of the electrolyte solution penetrating into the separator housed in the shell tube 1 to the outside of the battery. It is formed of an insulating material, for example, a synthetic resin material, in order to prevent shorts. The gasket 2 is formed in an annular shape, and an annular vertical annular portion 13 is provided at the periphery.

An explosion-proof valve 3 is provided on the gasket 2 above. The explosion-proof valve 3 is made of aluminum, nickel or an alloy thereof, and has a disk shape having a diameter slightly shorter than the diameter of the gasket 2, and an annular vertical annular portion 13 provided in the gasket 2. It is inserted in the inner circumference side of). In addition, the explosion-proof valve 93 has an annular end 64 slightly inward of the inner end of the gasket 2, and has an annular ridge 3b projecting downward to the portion hung from the end 40. Has In addition, the center portion has a projection 3a projecting downwardly from the ridge 3b, and between the ridge 3b and the projection 3a, the upper surface thereof is radial near the bottom of the projection 3a. It has a thin thickness portion 15 formed into a groove.

In addition, the stripper 4 provided below the explosion-proof valve 3 is formed of a material such as aluminum, and has a through hole 11 through which the protrusion 3a of the explosion-proof valve 3 penetrates in the center, and an insulating film on the upper surface thereof. 16 is deposited. The insulating film 16 is made of a nonwoven fabric, a polymer thin film, or a polymer coating film. And the lead board 8 is welded to the lower surface of the projection part 3a so that the lower surface of the stripper 4 and the lower surface of the projection part 3a may bridge | bridge each other. Moreover, the outer peripheral part of the edge part 14 of the explosion-proof valve 3 becomes the flat part 3c, The surface of this flat part 3c and the flat part of the closed lid 5 mentioned later connect each other, and the lead terminal 9 ), The lead plate 8, the explosion-proof valve 3, and the closing lid 5 are electrically connected.

Further, the outer peripheral portion of the explosion-proof valve 3 as the flat portion 3c deforms downward when the explosion-proof valve 3 is caulking the battery, so that the deformation is absorbed by the flat portion 3c, and the thin portion is thick. This is to avoid affecting (15).

In addition, an occlusion cap 5 is provided above the explosion-proof valve 3 so as to face the explosion-proof valve 3. The closure lid 5 is a positive electrode terminal, has a disc shape slightly smaller than the diameter of the explosion-proof valve 3, and is accommodated in the blade portion 17 provided at the main end of the explosion-proof valve 3. In the center part, the protrusion part 18 protruding upward of this battery is formed. The closure lid 5 is formed of a hard metal material, and is formed of a stainless plate in this example, thereby increasing the strength of the battery. In addition, two gas discharge holes 19 and 20 are drilled through the protruding portion 18 of the closure lid 5.

The gasket 2, the explosion-proof valve 3 and the closing lid 5 are caulked from the outer peripheral portion of the outer tube 1 toward the axis of the battery. In addition, as mentioned above, the explosion-proof valve 3 with a caulking, the closing lid 5, and the outer tube 1 are integrated via the gasket 2, and this battery is insulated. That is, the gasket 2 is provided with a vertical annular portion 13 at its periphery, and an explosion-proof valve 3 and a closing lid 5 are disposed in the vertical annular portion 13, and the vertical annular portion 13 is disposed. Since the circumferential wall portion 12 of the outer shell 1 is located at the outer circumference of the shell), caulking in the axial direction of the battery from the outer circumference of the outer shell 1, the outer tube 1 and the explosion-proof valve 3 and the closing lid The gasket 2 is sandwiched between (5) and the battery is sealed.

Therefore, the said gasket 2 makes insulation with the explosion-proof valve 3, the closing lid 5, and the exterior pipe 1 connected with the lead terminal 9 of an anode.

Next, as a result of performing an overcharge test on the battery relating to the present embodiment configured as described above, it became as shown in FIG. 6 and FIG.

That is, as shown in FIG. 6, as charging progresses, the battery voltage (curve I) increases, and the battery temperature (curve III) also increases. As the overcharged state progresses, gas is generated and filled by chemical change of the power generating element, and the internal pressure of the battery begins to rise due to the filling of the gas, and the explosion-proof valve 3 is deformed by the increase of this internal pressure. As shown in FIG. 7, the projection part 3a of the explosion-proof valve 3 is pushed in the direction of internal pressure, ie, the direction of the closure lid 5, and moves upwards. By moving upward of the projection part 3a, the lead plate 8 welded to the lower surface of the projection part 3a ruptures in the welding part, and the charging current (refer to curve II in FIG. 6) becomes Is blocked. The interruption of this current is performed at the time when the gradient of the battery temperature starts to rise on the graph of FIG. 6, after which the drop of the battery temperature starts, and abnormality such as battery ignition, rupture, leakage of electrolyte solution is prevented.

As described above, according to this example, before the time when the conventional safety valve is operated, that is, the progress of abnormal reaction such as decomposition in the battery, the current can be stopped and stopped during the initial stage, and ignition and rupture can be prevented. have.

In addition, since the reaction can be stopped before the explosion-proof valve 3 is opened, leakage of the electrolyte solution from within the battery can also be reduced.

Similarly, even when an external short circuit occurs due to battery misuse, the current is cut off at the initial stage of the temperature rise due to the short circuit current, thereby preventing the battery from igniting, rupturing or leaking the electrolyte.

In addition, when the gas generate | occur | produces in a large quantity from the electric power generation element as charging progresses extremely, etc., the thin thickness part 15 of the explosion-proof valve 3 cleaves and guides gas to the obstruction lid 5 direction, The gas is exhausted into the atmosphere via the gas discharge holes 19 and 20.

7 shows an example in which the lead plate 8 is ruptured and the current is cut off by the ridge of the protrusion 3a due to internal pressure. The lead plate 8 is not ruptured. There may be a case where the electrical connection is cut off as the projection 3a is peeled off the welded portion.

In addition, in the said embodiment, although the radial groove was formed as the thin thickness part 15 of the explosion-proof valve 3, it is not limited to this, A some groove may be formed concentrically, and a wide annular groove is provided. One or two may be formed.

In the embodiment, a projection 3a projecting downward in the center of the explosion-proof valve 3 is provided, and the projection 3 is inserted into the through hole 11 of the stripper 4, and then In the lower surface, the lead plate 8 was passed on the lower surface of the stripper 4 and the lower surface of the projection 3a to be welded to the lower surface of the projection 3a. However, as shown in FIG. 8, the explosion-proof valve 3 The lead plate 8 may be deformed into a trapezoidal shape, and the top portion thereof may be welded to the center lower surface of the explosion-proof valve 3. Also in this case, it is preferable to provide the thin-walled part 25 similar to 1st Example in the explosion-proof valve 3.

In the first and second embodiments, the safety valve device is installed on the upper side of the outer tube 1, that is, on the anode side. The lower part of the outer tube 1, as in the third embodiment shown in FIG. In other words, it may be provided on the cathode side. In this third embodiment, the lower surface portion 11A of the outer tube 1 is molded into the shape opposite to the explosion-proof valve 3 used in the first embodiment, and the side that contacts the outer tube 1 in the interior thereof. The stripper 130 having the insulating film 134 is provided in the same manner as in the first embodiment, and the lead wave 131 of the outer tube lower surface portion 11A is directed upward from the through hole 132 of the stripper 130. The lead terminal 133 which welds to the upper surface of the projection part 11a, constitutes the upper surface of the stripper 130, and the projection part 11a of the lower surface part 11A of the outer tube as mutually, and extends from the lead plate 131. One end of is attached with a cylindrical wound cathode.

Although not shown, the bottom face 11A of the outer tube 3 of the third embodiment is formed in a flat plate shape as in the second embodiment, and the lead plate 131 is deformed into a U-shape so that the bottom portion of the outer face tube ( You may make it weld to the center upper surface of 11A).

Next, the example which improved the assembly workability of the above-mentioned current cutoff valve is demonstrated.

That is, in the above-described battery, the insulating film 16 is placed on the explosion-proof valve 3, and the lead stiffening 4 is placed again, and then the protrusions 3a and the lead plate 8 of the explosion-proof valve 3 It is assembled by performing welding. Since these components are usually incorporated into a cylindrical battery having a diameter of about 10 to 20 mm, for example, they are considerably smaller. Therefore, handling of these parts during assembly work is complicated, and in particular, these parts assembled with carelessness when incorporated into a battery are easily decomposed, and thus there is room for improvement in workability, which is a problem in mass production. This hinders productivity improvement.

Hereinafter, the Example which improved assembly workability is demonstrated with reference to FIGS. 10-13. In addition, the same code | symbol is attached | subjected to the same part as the Example shown in FIG. 5, and the description is abbreviate | omitted.

10A and 10B are longitudinal cross-sectional views of the safety device 25 installed inside the battery.

In FIG. 10A and FIG. 10B, the explosion-proof valve 3 has the annular end part 14 between the outer peripheral plane part 3c and the center plane part 3d. The center plane portion 3d is formed in a flat plate shape except that the protrusion 3a and the thin groove 15 are provided. By fastening at the bottom of the annular end portion 14, an annular groove 14a is formed on the outer circumferential surface of the end portion 14, so that the annular protrusion protrudes outward from the groove 14a. The projection 14b of the phase is formed.

The intermediate fitting body 30 has a disk shape, the upper surface of which has a central plane portion 30d of the explosion-proof valve 3 and a through hole 11 extending in the vertical direction at the center thereof. It corresponds to the upper surface of the disk-shaped lead stripper 4, respectively. And the outer periphery of the intermediate fitting body 30 is provided with the annular vertical annular part 33 so that it may protrude on the upper surface side and the lower surface side, respectively. On the inner circumferential surface of the vertical annular portion 33a on the upper surface side of the vertical annular portion 33, an annular groove 30b and an annular projection portion 30a projecting slightly in the center direction compared to the groove 30b are respectively. Formed. In addition, four thick vertical annular portions 33b on the lower surface side of the vertical annular portion 33 are intermittently formed as shown in FIG. 12B. And the inner peripheral surface of this intermittent thick vertical annular part 33b is similarly intermittent annular groove 30d, and similarly intermittent annular projection which projects slightly toward the center direction compared with this groove 30d. 30c is formed, respectively. Moreover, the thickness of the vertical annular part 33b of the thickness of the lower surface side of the intermediate fitting 30 is formed thicker than the thickness of the vertical annular part 33a of the upper surface side, and the radius of the annular groove 30d is This thickness is smaller than the radius of the annular groove 30b.

11, the cross section of the II-II line of FIG. 10A of the said safety device 25 is shown. In FIG. 11, the intermediate fitting body 30 has a central hole 31 in its center that is larger than the through hole 11 of the lead stripper 4, and is also perpendicular to the point symmetrical position with respect to the center. A plurality of substantially semicircular through-holes 32 having the inner circumferential surface of the annular portion 33b as the center of the knot circle are provided. Then, as shown in FIG. 12B, the ventilation holes 32 are formed between the vertical annular portions 33b having a thickness on the intermittent lower surface side, and the thin thickness on the lower surface side is cut out on the inner circumferential surface thereof. The vertical annular portion 33c is formed intermittently, and the lower surface side vertical annular portion of the annular shape is formed by the thick vertical annular portion 33b and the thin vertical annular portion 33c. Therefore, the thickness of the lower surface side vertical annular part 33c in which the inner peripheral surface is cut out is formed considerably thinner than the thickness of the vertical annular part 33b. Moreover, about the vertical annular part 33a of the upper surface side, even if the ventilation hole 32 exists, it is formed in the same shape over the whole circumference with the projection part 30a and the groove | channel 30b.

When the ventilation holes 32 as described above are provided in the intermediate fitting body 30, when the lead stripper 4 is inserted into the lower surface side of the intermediate fitting 30, the outer peripheral surface of the lead stripper 4 ( A large gap 35 is formed between 4a) and the inner circumferential surface of the vertical annular portion 33c as shown in FIG. 12C, so that the gap 35 and the vent hole 32 communicate with each other. Therefore, the battery internal pressure is sufficiently applied to the center plane portion 3d of the safety valve 3.

The intermediate fitting body 30 may be made of a synthetic resin having elasticity such as PBT (polypropylene terephthalate), PP (polypropylene), PEEK (polyether ketone), and the like. The insulating film 16 made of a nonwoven fabric or the like in the case of the embodiment shown in FIG. 5 is unnecessary.

The safety valve 3, the intermediate fitting body 30, the lead stripper 4, and the lead plate 8 comprised as mentioned above are assembled as follows. That is, the intermediate fitting body 30 is placed on the safety valve 3 having the protrusion part 3a, and pressed slightly to the intermediate fitting body 30, as shown in FIGS. 10A and 10B. The projection part 30a of this is fitted into the unevenness | corrugation in the groove | channel 14a of the safety valve 3 past the projection part 14b of the safety valve 30. Therefore, with the safety valve 3 shown by the solid line in FIG. It is integrally combined with the intermediate fitting body 30 shown by a dashed-dotted line.

Next, the lead stripper 4 is placed on the intermediate fitting body 30 and pressed slightly strongly, so that the outer circumferential surface 4a of the lead stripper 4 moves the projection 30c of the intermediate fitting body 30. The concave-convex fitting is pasted to the groove 30d of the intermediate fitting body 30. Therefore, the safety valve 3 shown by the solid line in FIG. 12B, and the lead stripper 4 shown by the dashed-dotted line are integrally couple | bonded via the intermediate fitting body 30 shown by the solid line. In this case, it goes without saying that the safety valve 3 can be unevenly fitted after the lead stripper 4 is unevenly fitted to the intermediate fitting body 30. Thus integrated safety valve 3 and lead stripper 4 are not easily detached from the intermediate fitting body 30 in normal handling. Next, the lead plate 8 shown by the dashed-dotted line in FIG. 12C is ultrasonically applied to the protrusion 3a of the safety valve 3 whose top part is opposed through the through hole 11 of the lead stripper 4. It is attached by welding or the like.

Next, an operation in which the safety device 25 cuts off the current in response to the increase in the internal pressure will be described with reference to FIG. When the battery internal pressure is raised due to the above-described causes, the battery internal pressure is transmitted to the central flat portion 3d of the safety valve 3 via the gap 35 and the vent hole 32. Since the safety valve 3 is fixed together with the lid 5 in the outer circumferential plane portion 3c, when the battery internal pressure reaches a predetermined value, as shown in FIG. 13, the relief portion 3 includes the projection portion 3a. The center portion is lifted upward. Therefore, the lead plate 8 at least partially peels off the safety valve 3 at the welded portion on the projection 3a or the current itself is ruptured.

As described above, the safety valve 3 and the lead stripper 4 can be simply fitted into the intermediate fitting body 30 by unevenness, and these are combined together so that they are not easily separated, so assembling work of the safety device. This too becomes easy. Moreover, since the lead stripper 4 is fixed to the safety valve 3, the work which welds the lead plate 8 to the lead stripper 4 also becomes easy. Therefore, since the workability is much improved at the time of assembling the assembly, and the assembly can be accurately assembled as prescribed, the operation of the safety apparatus is assured and the reliability thereof is high.

In addition, in the above-mentioned embodiment, although the thin plate-shaped lead plate 8 was used as a lead, a linear or other arbitrary shape can be used.

By installing such a current blocking valve in the secondary battery, however, it is possible to avoid the breakdown of the battery due to the increase in the internal pressure due to the decomposition of the electrolyte. However, the case where the increase in the internal pressure does not depend solely on the decomposition of the electrolyte has been studied. need.

As an example, an organic electrolyte secondary battery using LiCoO ₂ as a cathode active material will be described.

That is, first, lithium and cobalt composite oxide (LiCoO ₂ ) as a cathode active material are synthesized as follows. Commercially available lithium carbonate powder (Li ₂ O ₃ ) cobalt carbonate (CoCO ₃ ) was weighed so that the ratio of lithium atoms and cobalt atoms was 1: 1, sufficiently mixed using a vibration mill, and then used in an air atmosphere in an air furnace at 900 ° C. It is calcined for 5 hours, and then pulverized using auto trigger to obtain a LiCoO ₂ powder.

The X-ray diffraction pattern of the obtained LiCoO ₂ is shown in FIG. From this X-ray diffraction pattern, it was confirmed that what was produced by the above production method was consistent with LiCoO ₂ of a Joint Committee on Powder Diffraction Standards (JCPDS) card widely used as a standard for powder X-ray diffraction data.

Next, the anode 71 is made as follows. The above-described synthesized lithium and cobalt composite oxide (LiCoO ₂ ) was used as the positive electrode active material, and 6 parts by weight of graphite as the conductive material and 3 parts by weight of polyvinylidene fluoride as the binder were used in 91 parts by weight of the positive electrode active material. Add and mix to make a positive electrode mixture. And the positive electrode mixture is dispersed in solvent N-methyl-2-pyrrolidone to obtain a slurry. Next, these positive electrode mixture slurries are uniformly applied to both surfaces of the strip-shaped aluminum foil serving as the positive electrode current collector, and then dried by compression molding with a roller press to obtain a strip-shaped positive electrode 71.

In addition, the cathode 72 is made as follows. Pulverized pitch coke is used as a negative electrode active material, 90 parts by weight of this pitch coke and 10 parts by weight of polyvinylidene fluoride as a binder are added and mixed to prepare a negative electrode mixture. The negative electrode mixture is dispersed in solvent N-methyl-2-pyrrolidone to obtain a slurry. Next, this negative electrode mixture slurry is uniformly applied to both surfaces of a strip-shaped copper foil as a negative electrode current collector and dried. After drying, compression molding is carried out by a roller press to obtain a strip-shaped cathode 72.

Next, a pair of separators 73a and 73b made of a band-shaped anode 71, a band-shaped cathode 72, and a microporous polypropylene film having a thickness of 25 µm was formed with a cathode 72 and a separator 73a. ), The positive electrode 71, and the separator 73b are laminated in this order, and then the laminated body is wound on the core 21 in a spiral winding multiple times to produce a wound body.

Then, using the wound body and the nonaqueous electrolyte (obtained by mixing propylene carbonate containing 1 mol / L of lithium hexafluorophosphate and 1.2-zimethoxyethanol), the current interruption was the same as that shown in FIG. A nonaqueous electrolyte secondary battery having the device 25 can be manufactured. In this case, the nonaqueous electrolyte secondary battery can be, for example, a cylindrical shape having a diameter of 20.5 mm and a height of 42 mm, and can be used at a voltage of about 4.1 V when charged normally.

By the way, if the 20 nonaqueous electrolyte secondary batteries were produced, and these were charged for 2 hours at a current of 2 A and overcharged, 18 (90%) cells were exothermic with a rapid temperature rise or relatively rapid breakage. Showed a damage condition.

The present inventors earnestly investigated this cause, and the following turned out. That is, when the nonaqueous electrolyte secondary electrolyte secondary battery as described above is overcharged and the battery voltage is about 4.8 V, the positive electrode active material (LiCoO ₂ ) is decomposed to generate oxygen gas. This oxygen gas reacts rapidly and differently with lithium in the negative electrode so that the current falls into the above-mentioned damage state. As shown by reference in FIG. 20 to be described later, when the battery voltage is about 4.8 V, the battery breakdown voltage does not increase very much. Therefore, before the above-mentioned current interruption device operates, an abnormal reaction between oxygen gas and lithium in the negative electrode proceeds rapidly.

As a countermeasure against such overcharging of a secondary battery, in addition to providing a current interruption means in the battery itself as described above, there is provided an overcharge preventing function, for example, in the charging device of the secondary battery. However, considering, for example, charging with a charging device that does not have such a prevention function, it is important for safety measures that the current interruption means can be operated reliably. An object of the present invention is to provide a nonaqueous electrolyte secondary battery in which the current interrupting means reliably operates even when the nonaqueous electrolyte secondary battery having the current interrupting means is overcharged.

In order to achieve the above object, the present invention provides a positive electrode using a lithium compound as the positive electrode active material, a negative electrode capable of doping and undoping lithium, a nonaqueous electrolyte, and a current blocking means operating in accordance with an increase in the internal pressure. In an equipped nonaqueous electrolyte secondary battery, the positive electrode active material is mainly composed of a first active material and a second active material, and the first active material is mainly composed of a first active material and a second active material. Wherein the first active material consists of L _ix N _iy Co _1-y O ₂ (where 0 × ≦ 1 and 0 ≦ y 0.50) The active material of ₂ consists of L _ix N _{iy '} , Co _1-y' O ₂ , provided that 0 x '≦ 1 and 0.50 ≦ y' ≦ 0.90.

The second active material is 100 parts by weight of the total cathode active material, preferably 0.5 to 70 parts by weight, more preferably 2 to 50 parts by weight.

In addition, one type of said 1st or 2nd active substance does not need to be one each, and you may use together two types or more types of them in the range which satisfy | fills the said conditions, respectively.

In addition, as the negative electrode active material of the negative electrode, a conductive polymer such as polyacetylene, a carbonaceous material such as coke, etc. can be used in addition to metal lithium and a lithium alloy, all of which can dope and dedope lithium. As the nonaqueous electrolyte, for example, a nonaqueous electrolyte in which lithium salt is used as an electrolyte and dissolved in an organic solvent (nonaqueous solvent) can be used.

Here, as the organic solvent, for example, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofran, 1,3-dioxolane, 4-methyl Or a mixture of two or more kinds of solvents such as 1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile and propionitrile. Electrolytes can be used as well known in the art, LiClO 4, LiAsF ₆ , LiPF ₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li and the like .

As the current interrupting means, the current interrupting device of the battery described with reference to FIGS. 5 and 7 can be used, but the present invention is not limited to this, and the electric current interrupting device can be interrupted in accordance with the increase in the battery breakdown voltage.

In a nonaqueous electrolyte secondary battery in which a positive electrode active material composed mainly of the first active material and the second active material is used for the positive electrode, when the battery voltage is increased due to overcharge, the second active material has a catalytic action. Therefore, the decomposition of the nonaqueous electrolyte is promoted, so that gas is generated. Therefore, the battery internal pressure is relatively gently increased by the decomposition gas of this nonaqueous electrolyte. The decomposition voltage generated by this decomposition gas is not a high voltage such that the positive electrode active material decomposes to generate oxygen gas, and the oxygen gas reacts rapidly with lithium in the negative electrode. There is no damage, and the current interruption means reliably operates due to an increase in the battery internal pressure. Therefore, abnormal reaction in the battery due to overcharge can be prevented.

EXAMPLE

EMBODIMENT OF THE INVENTION Hereinafter, the Example to which this invention is applied is demonstrated with reference to FIG. 5, 7, 14-14.

In this case, except that the structure of the positive electrode activity of the positive electrode 71 is different, the nonaqueous electrolyte secondary battery with a current interruption device was produced in the same manner as in the above-described example. And the anode 71 was made as follows.

That is, lithium and cobalt complex oxide (LiCoO ₂ ) described in the reference example in which x is almost 1 and y is 0 in Li _x Ni _y O _1-y O ₂ were used. As the second active material, lithium, nickel and cobalt complex oxides (LiNi _0.9 Co _0.01 O ₂ ) having almost 1 and y of 0.9 in Li _x Ni _y Co _1-y O ₂ were synthesized and used as follows.

Commercially available lithium carbonate powder (Li ₂ Co ₃ ), nickel carbonate powder (NiCo ₃ ) and cobalt carbonate powder (CoCO ₃ ) were weighed so that the ratio of lithium atoms, cobalt atoms and nickel atoms was 1: 0.1: 0.9, and vibrated. The mixture was sufficiently mixed with wheat, and then calcined at 900 ° C. for 5 hours using an electric furnace in an air atmosphere, and then pulverized using an automatic mortar to obtain LiNi _0.9 Co _0.1 O ₂ powder.

In addition, below, the value of x in Li _x Ni _y Co _1-y O ₂ is almost 1 unless otherwise indicated.

A mixture obtained by mixing 90% by weight of LiCoO ₂ and 10% by weight of Ni _0.9 Co _0.1 O _{2 is} used as the positive electrode active material, and the current interruption device shown in FIG. A nonaqueous electrolyte secondary battery having 25) was produced. This battery is referred to as battery 1 for convenience, as shown in the first table described later.

In addition, in order to confirm the effect of this invention, in the above-mentioned Li _x Ni _y Co _1-y O ₂ , when lithium, nickel, and cobalt composite oxide which changed the value of y to 0.3, 0.5, 0.7, 1.0 were mentioned above, Synthesis was carried out in the same manner as in.

Although the x-ray diffraction patterns of the complex oxides are shown in FIGS. 15 to 19, the y values of the lithium, nickel, and cobalt complex oxides Li _x Ni _y Co _1-y O ₂ synthesized as described above are different. , the x-ray diffraction pattern (FIG. 14) shown at the time of the basic composition of LiCoO ₂ whose y = 0 is not changed, but only the surface spacing is changing according to the value of y. In other words, the crystal structure is the same as LiCoO ₂ and Li _x Ni _y Co _1-y O ₂ , but it can be said that the materials have different interlayer distances.

In addition, lithium, nickel, and cobalt composite oxides are not limited to the above-described synthesis examples, and can be similarly obtained even when they are synthesized by firing with each hydroxide or oxide of lithium, nickel, cobalt, and the firing temperature is 600. To 900 ° C.

The above-mentioned five kinds of lithium, nickel, and cobalt composite oxides were used alone as the positive electrode active material, and thus the nonaqueous electrolyte secondary battery AF shown in Table 1 was produced in the same manner. In addition, a mixture obtained by mixing the lithium, nickel, cobalt composite oxide and lithium, cobalt composite oxide (LiCoO ₂ ) in the weight ratio shown in the first table is used as a positive electrode active material to produce a nonaqueous electrolyte secondary battery G, H, J, K was produced in the same way.

Here, secondary batteries H and I are examples according to the present invention, and secondary batteries A to G, J, and K are comparative examples.

Next, twenty nonaqueous electrolyte secondary batteries A to K were described. Then, the battery was charged with a current of 2 A for 2 hours to be in an overcharged state, and the incidence rate of damage to the battery, which caused rapid heat generation and relatively rapid breakage, was investigated. The results are shown in the first table. The same table also shows the case of the above-described reference example.

In order to investigate the ease of decomposition of the electrolytic solution, seven kinds of nonaqueous electrolytes in which LiNiCoO is used as a positive electrode active material, each of seven types of complex oxides of y = 0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0 in total are used alone. The battery voltage and the battery internal pressure at the time of overcharging were measured with respect to the secondary battery, and the result was shown in FIG. In addition, LiCoO whose y = 0 is a case of the conventional example. In addition, when each of the grounds with an increased internal pressure of the battery was decomposed and the generated gas was collected and analyzed, the generated gas was decomposed and the generated gas was decomposed and analyzed. Therefore, it can be said that the increase in the battery internal pressure in FIG. 20 is due to decomposition gas of the electrolyte solution. From Fig. 20, the larger the value of y in LiNiCoO is, the more likely the decomposition gas is to be generated. Therefore, the decomposition voltage of the electrolyte decreases as the value of y increases. That is, in each case of LiCoO (conventional example) with y = 0, LiNiCoO with y = 0.1 and LiNiCoO with y = 0.3, the decomposition voltage is around 4.8V. In the case of LiNiCoO with y = 0.5, LiNiCoO with y = 0.7 and LiNiCoO with y = 0.9, the decomposition voltage is around 4.5V. In the case of LiNiO with y = 1.0, the decomposition voltage goes down to about 4.0V.

These lithium, nickel, and cobalt composite oxides are thought to have a catalytic effect that accelerates the decomposition of the electrolyte.

Based on the conclusions of FIG. 20, the incidence of battery loss of the batteries A to K in Table 1 shows that the batteries C, D, E, F, H, I, which contain LiNiCoO with y of 0.5 or more as a positive electrode material. It is clear that J is not damaged at all. That is, only a small amount of lithium and cobalt composite oxides containing no nickel was found to have the effect, and it was confirmed that the voltage at which the battery breakdown voltage started to rise, that is, the decomposition voltage of the electrolyte solution was lowered.

In addition, batteries A, B, G, and K, which contain LixNiCoO with y less than 0.5 as a positive electrode active material, cause considerable damage as in the reference example. That is, it can be said that LiNiCoO with y of less than 0.5 is not very expected to have the catalytic effect.

In addition, the batteries containing LiNiO with y = 1.0 as a positive electrode active material, F, J are not damaged, but the battery voltage at the initial stage of charging is still low, and the electrolyte voltage is decomposed to increase the internal voltage. It was confirmed that the shutoff device was working and could not actually be used as a battery.

In addition, the use of LiNiCoO alone as a positive electrode material of a nonaqueous electrolyte secondary battery like a battery, C, D, and E is disclosed in Japanese Patent Laid-Open No. 63-299056. When comparing LiNiCoO (y = 0) and LiCoO as the positive electrode active material, the former has a lower discharge voltage and a lower energy density, especially when the value of y is larger than that of the latter. do.

The cells H and I can use LiCoO, which has a high discharge voltage, as a positive electrode active material, and the current blocking device reliably operates before the battery becomes damaged and reaches a high charge voltage, and the battery generates heat rapidly or breaks relatively rapidly. It was confirmed that it was not in a damaged state.

Comparing the batteries H and K, it can be seen that even though the molar ratio of nickel to cobalt in the positive electrode active material is almost the same, the incidence of battery loss is a completely different result.

From the above results, the decomposition of the electrolyte occurs at about 4.6 V or more, which is not preferable because the decomposition of the electrolyte occurs simultaneously with the decomposition of the electrolyte during overcharging, and oxygen is generated, and the oxygen reacts rapidly with lithium in the cathode. In addition, if decomposition of the electrolyte occurs at 4 V or less, the electrolyte is decomposed even under normal charging, and the current interruption device is operated, which is not preferable.

That is, if the y value of lithium, nickel, and cobalt composite oxide LiNiCoO (0.2 ≦ x ≦ 1) is mixed in the positive electrode active material in the range of 0.50 to 0.90, the electrolyte is decomposed at an appropriate voltage and is simply The molar ratio of nickel and cobalt alone does not determine the decomposition voltage of the electrolyte. When the lithium, nickel, and cobalt composite oxides are contained in 0.5 wt g, more preferably 2 wt%, of the total positive electrode active material, the effect is exhibited. The voltage is not so low. Moreover, a small amount of LiMnO etc. may be contained as another positive electrode material.

As the first positive electrode active material, in addition to LiCoO described above, it is also possible to use LiNiCoO (0 x ≤ 1, preferably 0.2 ≤ x ≤ 1) which is 0 y 0.5. In addition, although the present embodiment was applied to a spiral wound cylindrical secondary battery, the shape is not particularly limited as long as it is a nonaqueous electrolyte secondary battery equipped with a current interrupting means that operates by the rise of the battery intercalation. The nonaqueous electrolyte may be a solid, in which case a conventionally known solid electrolyte can be used.

Claims (1)

A container having a power generator formed of a positive electrode, a negative electrode, a separator inserted between the positive electrode and the negative electrode, and an electrolyte solution in itself, an explosion-proof valve for enclosing the container, and one end of the positive or negative electrode An electrical lead connected to any one of which is connected to the explosion-proof valve, and a stripper element provided between the generator and the explosion-proof valve, the explosion-proof valve being configured to increase the internal pressure of the container. And deform and the stripper element holds the electrical lead on one side of the generator to remove the electrical lead from the explosion-proof valve upon deformation of the explosion-proof valve.

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